May. 29, 2012

The brown mouse lemur (Microcebus rufus) is one of the smallest primates in the world. It also has the distinction of being the only animal that is parasitized by Lemurpediculus verruculosus, a blood-sucking louse that recently found itself at the center of a scientific effort to map the social network of its elusive host.

The study, published in the journal BMC Ecology, was conducted in southeastern Madagascar, at Ranomafana National Park, which is home to the brown mouse lemur. Like other mouse lemurs, this species, which is also known as the rufous mouse lemur, is arboreal and nocturnal, and researchers who want to know more about it have been continually frustrated but its elusive character. But in an unusual twist, a team of Finnish and U.S. scientists turned to L. verruculosus, using the louse as a tracking system to map the lemur's movement.

The researchers began by capturing brown mouse lemurs and searching them for lice. Lice found on the ears were given unique color identification codes consisting of varying patterns of dots of nail polish. Each lemur was then released. Upon recapture later, the animals were checked for the marked lice, and if present, the number of parasites and each parasite's location on the body was recorded. This approach allowed the team to determine whether and how the lice had been passed between individual lemurs and which individuals contributed most to the parasite's spread.

Of the 23 male and 9 female lemurs that the team successfully captured, 105 lice were marked and a total of 76 lice transfers were recorded. All the transfers occurred between just 14 of the males over a period of four weeks, coincident with the breeding season. The exclusive involvement of males led the researchers to conclude that contact between males, whether through breeding conflicts, nest sharing, or mating with females that had multiple male partners, served as the primary mode of louse transfer.

With their unique method of louse tracking, the team discovered that the spread of lice through brown mouse lemur populations is limited to the breeding season, when social contact between the animals increases substantially. This increase in turn accelerates the rate at which louse transfer occurs. In addition, by following the marked lice, the researchers discovered that the range of the brown mouse lemur extends over a much greater distance—providing the species with a much broader social network—than previously thought.

Similar to L. verruculosus, other species of sucking lice are specially adapted for life on a single host species, suggesting that the method of tracking used to determine L. verruculosus transfer among brown mouse lemurs could be applied for the investigation of social interactions among other elusive primates. In the process of gaining insight into primate social behavior, scientists may also uncover new information about parasite-host relationships and the dynamics of disease transmission among primates.

About Kara Rogers

Kara is a freelance science writer and senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is the author of Out of Nature: Why Drugs From Plants Matter to the Future of Humanity (University of Arizona Press, 2012).

The views expressed are those of the author and are not necessarily those of Science Friday.